U.S. patent number 6,798,357 [Application Number 10/247,399] was granted by the patent office on 2004-09-28 for method and system for collecting traffic information.
This patent grant is currently assigned to Navteq North America, LLC.. Invention is credited to M. Salahuddin Khan.
United States Patent |
6,798,357 |
Khan |
September 28, 2004 |
Method and system for collecting traffic information
Abstract
A system and method are disclosed for collecting traffic
information. One or more aircraft, such as helicopters, fly
predetermined flight paths above a geographic area. The flight
paths are determined so that portions of roads for which traffic
information are to be collected are within the ranges of remote
velocity sensors located on board the aircraft during the flights
of these aircraft along their respective flight paths. Each
aircraft includes positioning equipment that allows the precise
position (i.e., altitude, latitude, and longitude) and attitude
(i.e., roll, pitch, and yaw) of the aircraft during its flight to
be determined. During a flight along the predetermined flight path,
the remote velocity sensor in each aircraft is operated to perform
scans of locations on roadways in the geographic area. Using a
precise road map database and taking into account the location,
velocity and attitude of the aircraft while each scan is being
made, data indicating traffic conditions along the roadways are
collected.
Inventors: |
Khan; M. Salahuddin (Lake
Forest, IL) |
Assignee: |
Navteq North America, LLC.
(Chicago, IL)
|
Family
ID: |
32986990 |
Appl.
No.: |
10/247,399 |
Filed: |
September 19, 2002 |
Current U.S.
Class: |
340/989;
701/117 |
Current CPC
Class: |
G08G
1/0104 (20130101) |
Current International
Class: |
G08G
5/00 (20060101); G08G 001/123 () |
Field of
Search: |
;340/989,936,990,995.1,995.13 ;342/104,105,107,454,461
;701/117,118,119 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tweel; John
Attorney, Agent or Firm: Kozak; Frank J. Shutter; Jon D.
Kaplan; Lawrence M.
Claims
I claim:
1. A method of collecting data that indicate traffic conditions on
roads in a geographic area comprising the steps of: having an
aircraft fly a flight path over the geographic area; while said
aircraft is flying over the geographic area, scanning locations
along roads with a remote velocity sensing apparatus in said
aircraft to obtain data indicative of traffic conditions at said
locations; using a map database to identify the roads that
correspond to the locations scanned with the remote velocity
sensing apparatus; and associating the data indicative of traffic
conditions at said locations with corresponding identities of said
roads.
2. The method of claim 1 further comprising: filtering data
acquired by scanning to remove unwanted data readings.
3. The method of claim 2 wherein the filtering is performed in the
aircraft.
4. The method of claim 2 wherein the filtering is performed in a
base station to which the data acquired by scanning are sent.
5. The method of claim 1 further comprising: determining transit
times along the roads using the data indicative of traffic
conditions associated with said roads.
6. The method of claim 1 wherein said aircraft flies along said
flight path a plurality of successive times and further wherein
said locations are scanned during each of said plurality of
successive times to obtain data indicative of traffic conditions at
successive times.
7. The method of claim 1 wherein the aircraft is a helicopter.
8. The method of claim 1 wherein the aircraft is a lighter-than-air
aircraft.
9. The method of claim 1 further comprising: determining the
position of the aircraft while said aircraft is flying over the
geographic area.
10. The method of claim 1 wherein a plurality of aircraft are used
to obtain data indicative of traffic conditions throughout the
geographic area, wherein each of said plurality of aircraft flies a
separate different flight path over the geographic area.
11. The method of claim 1 wherein the flight path is
predetermined.
12. The method of claim 1 further comprising: using a detailed map
database in the aircraft to precisely aim the remote sensing
apparatus at the locations being scanned.
13. The method of claim 1 using a predetermined scan pattern to
precisely aim the remote sensing apparatus at the locations being
scanned.
14. The method of claim 1 further comprising: transmitting the data
indicative of traffic conditions at said locations from said
aircraft to a base station where the map database is used to
identify the roads that correspond to the locations scanned with
the remote velocity sensing apparatus.
15. The method of claim 14 wherein the base station receives data
indicative of traffic conditions from a plurality of aircraft each
of which flies a separate different flight path over the geographic
area and each of which scans locations along roads along its
respective separate flight path with a separate remote velocity
sensing apparatus located therein to obtain data indicative of
traffic conditions at said scanned locations.
16. The method of claim 1 wherein a relatively wide area is scanned
including the locations along the roads for which data indicative
of traffic conditions are sought as well as areas outside the
locations along the roads for which data indicative of traffic
conditions are sought, and wherein the method further comprises:
extracting from data obtained by scanning over the relatively wide
area the data that pertain to the locations along the roads for
which data indicative of traffic conditions are sought.
17. The method of claim 1 wherein the scanning is targeted at the
locations along the roads for which data indicative of traffic
conditions are sought to reduce scanning of areas other than the
locations along the roads for which data indicative of traffic
conditions are sought.
18. The method of claim 1 wherein said locations are in a direct
line-of-sight of said aircraft when said aircraft flies along the
flight path.
19. The method of claim 1 further comprising: providing traffic
information to drivers, wherein the traffic information corresponds
to the locations scanned with the remote velocity sensing
apparatus.
20. The method of claim 1 wherein said flight path comprises a
substantially stationary position.
21. The method of claim 1 further comprising: compensating for
movement of said aircraft relative to said flight path when aiming
the remote velocity sensor at the locations along the roads for
which data indicative of traffic conditions are sought.
22. The method of claim 1 wherein said aircraft is unpiloted.
23. A system for collecting information about traffic conditions on
roads in a geographic area comprising: an aircraft having airborne
traffic data collector components comprising: a positioning system
that determines a position of the aircraft while the aircraft is
flying; a remote velocity sensing apparatus; a stabilization
platform coupled to said remote velocity sensing apparatus; an
aiming apparatus that includes a real-motion compensating system,
wherein said aiming apparatus is coupled to said remote velocity
sensing apparatus and responsive to said positioning system and
wherein said aiming apparatus uses said real-motion compensating
system to aim said remote velocity sensing apparatus at specific
locations in the geographic area as the aircraft is flying along a
flight path; and an airborne communications system that transmits
data indicative of traffic conditions sensed by said remote
velocity sensing apparatus at said specific locations; and a base
station comprising: a land-based communications system that
receives the data indicative of traffic conditions sensed by the
remote velocity sensing apparatus in said aircraft; a geographic
database containing data that represent roads in said geographic
area including data that indicate locations of said roads; and a
data synthesis program that uses said geographic database to
associate the data indicative of traffic conditions received from
said aircraft with said roads.
24. The system of claim 23 wherein said base station receives data
indicative of traffic conditions sensed by each of a plurality of
aircraft each of which includes a separate set of airborne traffic
data collector components and wherein said data synthesis program
uses said geographic database to associate the data indicative of
traffic conditions received from each of said plurality of aircraft
with said roads.
25. The system of claim 24 wherein each of said plurality of
aircraft fly different flight paths.
26. The system of claim 23 wherein said flight path is
predetermined.
27. The system of claim 23 wherein said aircraft is a
helicopter.
28. The system of claim 23 wherein said aircraft is a
lighter-than-air aircraft.
29. The system of claim 23 wherein the remote velocity sensing
apparatus in said aircraft is a laser-based device.
30. The system of claim 23 wherein the remote velocity sensing
apparatus in said aircraft is a radar-based device.
31. The system of claim 23 wherein the remote velocity sensing
apparatus in said aircraft is a lidar-based device.
32. The system of claim 23 wherein said aircraft has an airborne
geographic database used by said aiming apparatus to determine said
specific locations at which to aim said remote velocity sensing
apparatus.
33. The system of claim 23 wherein said aircraft has data that
indicate a predetermined flight path along which said aircraft
flies while sensing traffic conditions.
Description
BACKGROUND OF THE INVENTION
The present invention relates to collecting information about
traffic along roads in a geographic area, and in particular, the
present invention relates to an efficient way for collecting
real-time traffic information.
Traffic information is used for various purposes. Commuters use
traffic information to plan their commutes to work. Trucking
companies use traffic information to plan routes that minimize
delays. Delivery companies use traffic information to determine
routes that are most efficient. Government agencies use traffic
information for emergency response purposes, as well as to plan new
highways and make other improvements.
There are different kinds of traffic information. Real-time traffic
information indicates the actual conditions that exist on roadways
at the present time. Historical traffic information indicates the
long-term average traffic conditions that have existed on roadways
over a period of time. There are also different types of traffic
information that are collected. For example, one important type of
traffic information relates to traffic incidents (e.g., accidents)
that have relatively short-term but significant effects. Other
important types of traffic information include traffic flow,
traffic volume, transit times, throughput and average speed.
There are various ways to collect traffic information. One way to
collect traffic information is to place sensors along roadways.
Another way to collect traffic information is to observe traffic
conditions from a tall building or aircraft (e.g., a traffic
helicopter). Still another way to obtain traffic information is to
have a number of vehicles travel along roads and report traffic
information back to a traffic information center.
Although these existing ways to collect traffic information are
satisfactory, there still exists room for improvements.
Infrastructure-based methods are associated with relatively high
deployment costs thereby limiting them to major roads.
Vehicle-based methods are associated with communications and
processing costs that have limited deployment of these methods as
well. Accordingly, it would be beneficial to have a method that
collects traffic information for a large number of roads
efficiently and reliably.
SUMMARY OF THE INVENTION
To address these and other objectives, the present invention
includes a system and method for collecting traffic information.
One or more aircraft, such as helicopters, fly predetermined flight
paths above a geographic area. These aircraft may be piloted or
remotely controlled. The flight paths are determined so that
portions of roads for which traffic information are to be collected
are within the ranges of remote velocity sensors located on board
the aircraft during the flights of these aircraft along their
respective flight paths. Each aircraft includes positioning
equipment that allows the precise position (i.e., altitude,
latitude, and longitude) and attitude (i.e., roll, pitch, and yaw)
of the aircraft during its flight to be determined. During a flight
along the predetermined flight path, the remote velocity sensor in
each aircraft is operated to perform scans of locations on roadways
in the geographic area. Taking into account the location, velocity
and attitude of the aircraft while each scan is being made, data
indicating traffic conditions from the scanned output are matched
to a precise road map database and the traffic flows on every
scanned road are thereby collected.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration of a geographic area in which an
embodiment of the present system is used to collect traffic
information.
FIG. 2 is a block diagram of some of the components in one of the
aircraft shown in FIG. 1.
FIG. 3 is a block diagram of some of the components in the base
station shown in FIG. 1.
FIG. 4 shows the geographic area of FIG. 1 with flight paths for
the aircraft.
FIG. 5 is a flowchart showing steps in a process for collecting
traffic information using the system of FIG. 1.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
I. Overview
FIG. 1 shows a geographic area 10. The geographic area 10
corresponds to a metropolitan region or a portion thereof.
Alternatively, the geographic area 10 may correspond to a region of
a different size.
Located in the geographic area 10 is a road network 14. The road
network 14 includes different functional classes of roads. For
example, the road network 14 may include freeways, major highways,
major business roads, minor business roads, residential streets,
alleys, and rural roads.
A traffic collection system 20 collects information about traffic
conditions on the road network 14. The traffic collection system 20
includes several components. According to one embodiment, the
traffic collection system 20 includes a base station 22, traffic
collection components located in one or more aircraft 26 and a
communications network 28 that enables the traffic collection
components located in the aircraft to communicate with the base
station 22.
(In a preferred embodiment, the aircraft 26 are helicopters,
although in alternative embodiments other types of aircraft may be
used, including planes, gliders, drones, lighter-than-air craft,
balloons, blimps, dirigibles, etc. Alternatively, a combination of
different types of aircraft may be used.)
II. The Airborne Traffic Data Collector Components
Each of the aircraft 26 is equipped to collect traffic information.
Referring to FIG. 2, each aircraft 26 includes airborne traffic
data collector components 30. The airborne traffic data collector
components 30 include a combination of hardware and software.
The airborne traffic data collector components 30 include a remote
velocity sensing apparatus 32. The remote velocity sensing
apparatus 32 is capable of determining the speed (i.e., velocity)
of remotely-located moving objects. The remote velocity sensing
apparatus 32 uses any suitable technology for this purpose, such as
a pulse laser, microwave, lidar or Doppler radar, etc. The remote
velocity sensing apparatus 32 determines the velocity of
remotely-located objects by transmitting a beam (e.g., microwave,
coherent light, etc.) at the remotely-located object and measuring
a property of the reflected beam.
Coupled to the remote velocity sensing apparatus 32 is an aiming
apparatus 38. The aiming apparatus 38 controls the remote velocity
sensing apparatus 32 to direct the beam at various different
locations along the road network 14 as the aircraft 26 travels
through the geographic area 10. The aiming apparatus 38 operates
under computer control so that the remote velocity sensing
apparatus 32 can be precisely aimed at particular locations,
preferably at specific times. In one embodiment, the aiming
apparatus 38 is capable of directing the remote velocity sensing
apparatus 32 through a 360 degree scan around the aircraft 26 and
through an elevation of 90 degrees. The aiming apparatus 38
includes a telescopic lens 40 or other means for automatically or
manually aiming the remote sensing beam at objects several
kilometers away.
The remote velocity sensing apparatus 32 and the aiming apparatus
38 are mounted on a stabilization platform 44 in the aircraft 26.
The stabilization platform 44 includes equipment that stabilizes
the remote velocity sensing apparatus 32 and the aiming apparatus
38. The stabilization platform 44 uses inertial sensors, a
gyroscope, etc., to negate the effects of the movements of the
aircraft 26 so that the aiming apparatus 38 can aim the remote
velocity sensing apparatus 32 at precisely predetermined locations
and at precise times.
Located in the aircraft 26 is a positioning system 50. The
positioning system 50 includes equipment that enables the precise
position (e.g., latitude, longitude, and altitude) and attitude
(e.g., roll, pitch, and yaw) of the aircraft 26 to be determined
continuously while the aircraft 26 is flying. The positioning
system 50 may include a GPS (or DGPS), an altimeter, inertial
sensors, or a combination of these or of other types of
equipment.
The airborne traffic data collector components 30 in each aircraft
26 include a communications system 62. The communications system 62
is used by the airborne traffic data collector components 30 to
interface with the communications network 28 to send data to (and
receive data from) the base station 22. The communications system
62 is preferably a relatively high bandwidth system capable of
transmitting a relatively large amount of data to a ground station.
Suitable communications systems include GSM or GPRS, although other
systems can be used.
The airborne traffic data collector components 30 in each aircraft
26 also include a synchronization program 66. The synchronization
program 66 is run on a suitable computer platform 68 located in the
aircraft 26. The synchronization program 66 is coupled to and
exchanges data with the remote velocity sensing apparatus 32, the
aiming apparatus 38, the stabilization platform 44 and the
positioning system 50.
In addition, the synchronization program 66 obtains data from an
on-board geographic database 70. The on-board geographic database
70 includes information about some or all the roads that form the
road network 14 in the geographic region 10. In particular, the
on-board geographic database 70 includes information about the
roads about which traffic flow information is to be collected along
the flight path of the aircraft 26. The on-board geographic
database 70 includes information that identifies the positions of
each of the roads represented therein. For example, in one
embodiment, the on-board geographic database 70 includes data that
identify points (e.g., latitude, longitude, and altitude) along
each of the represented roads. The on-board geographic database 70
may include other kinds of information. The on-board geographic
database 70 may include data about all the roads along the flight
path of the aircraft 26. Alternatively, the on-board geographic
database 70 includes data about only some of the roads, such as the
higher functional class roads, like freeways, major highways, and
possibly major and minor business roads.
The synchronization program 66 also uses flight path data 72 and a
scan pattern 73. The flight path data 72 indicate the path (i.e.,
series of positions) that the aircraft follows along its flight
path. The scan pattern 73 indicates the direction(s) (i.e.,
azimuth, elevation) at which to aim the remote velocity sensing
apparatus 32 for positions along the flight path. The
synchronization program 66 uses the flight path data 72 and the
scan pattern 73, in conjunction with data from the geographic
database 70 and data from the positioning system 50 and the
stabilization platform 44, to control the aiming apparatus 38 to
aim the remote velocity sensing apparatus 32 at precise locations
along the road network based on the relative positions of the
aircraft 26 along its flight path.
Another program included among the airborne traffic data collector
components 30 in each aircraft 26 is a processing program 74. The
processing program 74 is run on the computer platform 68 located in
the aircraft 26. Alternatively, the processing program 74 can be
run on another computer platform. The processing program 74
interfaces with the synchronization program 66.
The processing program 74 performs the steps of extracting
pertinent vehicle velocity data from the data received from the
remote sensing apparatus, matching the vehicle velocity data to a
precise digital map to identify the roads to which the data relate,
and filtering the vehicle velocity data. The extracting step
processes the data obtained by the remote velocity sensing
apparatus 32 to separate the data that indicate vehicle velocities
from extraneous data, such as data indicating stationary objects
like buildings or parked vehicles. The extracted velocity data
indicate discrete measurements of traffic flow at specific
locations along roads at specific times. Then, the processing
program 74 causes the road velocity data to be matched to a precise
digital map to indicate the precise locations on the road network
at which the remote velocity sensing apparatus was aimed. Then, the
data are filtered. There are several ways that the data can be
filtered. For example, a portion of a road may be scanned several
times within the span of several seconds. The filtering function
analyzes the data associated with these scans and, if they all
indicate approximately the same vehicle velocity along the portion
of road, redundant data readings are filtered out. According to
another example, during the flight of an aircraft along its flight
path, each road may be scanned at several different locations along
its length. If adjacent portions along a road have similar vehicle
velocity readings, a single velocity reading can be used for these
adjacent road portions. An advantage of filtering is that the
amount of data that need to be transmitted from the aircraft is
reduced.
The processing program 74 also causes the road velocity data
received from the remote velocity sensing apparatus to be
associated with a time stamp. Optionally, the processing program 74
also causes the road velocity data received from the remote
velocity sensing apparatus to be associated with reference-frame
data. The reference-frame data indicate the velocity, position,
orientation, etc., of the aircraft while the road velocity data are
being measured. In addition, the processing program 74 causes the
road velocity, time-stamp, and reference-frame data to be
temporarily stored on the aircraft 26 before being transmitted to
the base station 22. The computer platform 68 includes a suitable
data storage device or memory 78 for this purpose.
Another program among the airborne traffic data collector
components 30 in the aircraft 26 is a transmission program 82. The
transmission program 82 is run on the computer platform 68 located
in the aircraft 26 or alternatively, the transmission program 82 is
run on another computer platform. The transmission program 82
interfaces with the processing program 74 and the communications
system 62. The transmission program 82 sends the data collected by
the processing program 74 to the base station 22 using the
communications system 62. The transmission program 82 may send the
data continuously or alternatively, the transmission program 82 may
accumulate data and send the data in discrete portions. The
transmission program 82 may implement suitable compression or
compaction. The transmission program 82 may also provide for
suitable retransmission, error-handling, etc.
The airborne traffic data collector components 30 may include other
components in addition to those mentioned.
III. The Base Station
As mentioned in connection with FIG. 1, the traffic collection
system 20 includes a base station 22. The base station 22 is a
collection of hardware and software components. FIG. 3 shows some
of the components of the base station 22.
One of the components of the base station 22 is a communications
system 92. The communications system 92 interfaces with the
communications network 28 so that the base station 22 is capable of
receiving data from and sending data to the airborne traffic data
collection components 30 in each of the aircraft 26.
The base station 22 includes a traffic data synthesis and reporting
program 100. The traffic data synthesis and reporting program 100
is run on a suitable computer platform 110 at the base station 22.
The traffic data synthesis and reporting program 100 receives the
data transmitted from the aircraft 26, uses the data transmitted
from the aircraft 26 to determine traffic flow and other
information, such as transit times, and reports traffic information
to users. Operation of the traffic data synthesis and reporting
program 100 is described in more detail below.
IV. Setup
Before the traffic flow collection system (20 in FIG. 1) can be
used, flight paths for the aircraft 26 are determined. The flight
paths for the aircraft 26 are determined so that portions of each
road for which traffic information is to be collected are within
range of the remote velocity sensing apparatus located in at least
one of the aircraft at least once during the flight of the aircraft
along its flight path. More specifically, each of the aircraft
travels different flight paths. The different flight paths cover
the entire geographic area so that the traffic along the road
network across the entire area can be sensed by the equipment in at
least one of the aircraft. The predetermined flight paths are
selected so that significant portions of the roads for which
traffic data are to be collected are in a direct line-of-sight of
at least one of the aircraft during its flight along the
predetermined flight path associated therewith.
FIG. 4 shows examples of a plurality of flight paths 122, each
associated with a respective one of the plurality of aircraft
26.
The flight path for each aircraft 26 is determined based on several
factors. Some of these factors include:
1) the number of available aircraft that can operate at one
time;
2) the speed of the aircraft;
3) a path completion time;
4) the cyclic frequency for rescanning a given target location;
5) the miles of roads for which traffic information is to be
collected;
6) the flying altitude of the aircraft above ground level;
7) the geographic terrain of the area;
8) the road network of the geographic area;
9) the type of aircraft (e.g., helicopter, airplane, drone);
and
10) the size of the geographic area.
These various factors are used when developing flight paths. For
example, if more aircraft are available, the entire geographic area
can be covered more quickly (i.e., with shorter flight path
completion times). According to another example, if the terrain of
the geographic area is hilly, it may take more aircraft to cover a
geographic region of a given size because the hills may restrict
the line-of-sight for sensing of roads from the aircraft. There may
be additional factors that affect the determination of flight
paths.
Different geographic areas will require different flight paths.
Furthermore, over time, the flight paths for a geographic area may
be updated to take into account new roads or more detailed coverage
of existing roads.
According to one embodiment, flight paths are determined as
relatively wide swathes. This allows an aircraft following a flight
path to acquire all the necessary lines-of-sight with the portions
of roads for which data are being collected while making the flight
path relatively easy to follow. The width of a flight path swath is
determined taking into account various factors, such as the type of
aircraft, the terrain, etc.
When a flight path is determined, scan patterns for the flight path
can also be determined. As mentioned above, the scan pattern
indicates the directions and frequencies to aim the remote velocity
sensing apparatus for various positions along the flight path. In
one embodiment, the remote velocity sensing apparatus may be
operated with a full sweep scan pattern. With a full sweep scan
pattern the remote sensing apparatus is aimed sequentially in a
succession of parallel or otherwise regularly-offset paths to
create a scan pattern that completely covers a polygonal area on
the ground. When operated with a full sweep scan pattern, the
processing program in the aircraft extracts the pertinent vehicle
velocity data from a scan of the entire area. According to another
embodiment, a targeted scan pattern can be determined. With a
targeted scan pattern the remote sensing apparatus is aimed at only
the portions of roads for which vehicle velocity data are being
collected. According to the targeted scan pattern embodiment, the
directions to aim the remote sensing apparatus are determined based
on the lines-of-sight to various roads at the various positions
along the flight path. With the targeted scan pattern embodiment,
extracting the pertinent vehicle velocity data from the scans may
be facilitated.
Once the flight paths and associated scan patterns are determined,
data indicating each flight path and associated scan patterns are
provided to the respective aircraft. An aircraft may receive more
than one of the flight paths and associated scan patterns so that
alternative flight paths may be flown.
V. Operation
FIG. 5 shows parts of a process 150 for collecting traffic
information. As mentioned above, each aircraft 26 used by the
traffic information collection system 20 is associated with a
predetermined flight path (e.g., 122 in FIG. 4). To collect traffic
information, each of the aircraft 26 flies its predetermined flight
path (Step 160 in FIG. 5). In one embodiment, the aircraft pilot
operates the aircraft so that it follows its predetermined flight
path. In an alternative embodiment, the aircraft is equipped with
an automated pilot system (e.g., 166 in FIG. 2). According to this
alternative embodiment, the predetermined flight path for an
aircraft is provided to the automated pilot system 166 and the
automated pilot system 166 operates the aircraft so that it follows
its predetermined flight path.
Each of the aircraft may fly its predetermined flight path several
times. Alternatively, an aircraft may fly its predetermined flight
path only once. In another alternative, an aircraft may fly a
succession of different flight paths.
As each aircraft travels its predetermined flight path, the
position of the aircraft 26 is determined by the positioning system
50 located in the aircraft (Step 170 in FIG. 5). While following
the flight path, the processing program and the synchronization
program (74 and 66 in FIG. 2) cause the aiming apparatus 38 and the
remote velocity sensing apparatus 32 to sense vehicle velocities
along roads along the flight path in accordance with the scan
pattern 73 taking into account the aircraft position and attitude
(Step 180). The data may be filtered to remove the unwanted or
unnecessary data readings (Step 184). The on-board database 70 may
be used for this purpose. The data indicating the sensed vehicle
velocities are sent to the base station (Step 190). Optionally,
reference-frame data indicating the speed, location, and
orientation of the aircraft are also sent. (As mentioned above, the
data may be temporarily stored on the aircraft. The data may be
stored for several seconds or several minutes.)
At the base station 22, the traffic data synthesis and reporting
program 100 receives the data transmitted from each of the aircraft
26 (Step 200). Using a geographic database 210 located at the base
station, the data received from each aircraft are matched to
specific roads located in the geographic area 10 (Step 220). The
geographic database 210 includes information about some or all the
roads that form the road network (14 in FIG. 1) in the geographic
area 10, including information about the higher functional class
roads, such as freeways and major highways, and possibly about
major and minor business roads, residential roads, etc.
The geographic database 210 includes information that identifies
the positions of each of the roads represented therein. For
example, in one embodiment, the geographic database 210 includes
data that identify points (e.g., latitude, longitude, and altitude)
along each of the represented roads. The geographic database 210
also includes data that identify the name and/or highway
designation of each of the represented roads. The geographic
database 210 may include data that indicate the number of lanes
along each road, the widths of each road, the locations and widths
of lane dividers and medians, the locations of ramps,
intersections, bridges, tunnels, overpasses, etc. The geographic
database 210 also includes information about the legal posted speed
limit (or speed range category) at each point (or selected points)
along the represented roads. The geographic database 210 may
include other kinds of information.
As mentioned above, the data collected by each aircraft indicate
discrete measurements of traffic flow at specific points along
roads as measured remotely from the aircraft during its flight
along its flight path. The map matching process matches the data
received from the various aircraft to specific roads represented by
the geographic database and to specific locations along the roads.
The map matching process may be configured to match data for only
certain roads in the geographic area or for only certain categories
of roads.
After the data are matched to appropriate roads, the data for each
road are synthesized (Step 250). The step organizes the discrete
data measurements for each road being monitored. Each road may be
scanned several times at several different locations along its
length during a flight by an aircraft along its flight path. In
some cases, a road may be visible to more than one aircraft flying
along their flight paths, and if so, portions of the road may be
scanned by more than one aircraft. This step also takes into
account scans of roads from prior flights.
After the data for each road are synthesized, various traffic
parameters are calculated (Step 270). For example, transit times
can be calculated. As mentioned above, the processing program (74
in FIG. 2) in each aircraft also collects reference-frame data that
indicate the velocity, orientation, and position of the aircraft
while the road velocity data are being collected. Using the road
velocity data and the reference-frame data, transit times can be
calculated along each road. The transit time indicates the amount
of time it takes for a vehicle to transit a particular portion of a
road. In addition, other traffic information may be calculated,
such as the average speed, speed variance, flow variance, traffic
flow, etc.
After the various traffic parameters are calculated, traffic
reports are prepared (Step 280). These traffic reports can be
organized into various different formats. The traffic reports can
be sent directly to end users, e.g., vehicle drivers (Step 290).
Alternatively, the traffic reports can be sent to other entities
that use or combine the data in various ways. Some of these
entities may redistribute the traffic data directly or indirectly
to end users.
It is noted that the disclosed method for the remote collection of
vehicle velocity data may sometimes be affected by adverse weather
conditions. However, the disclosed method does not require direct
visual contact with the roads being monitored and the method can be
used under various conditions. The collection of vehicle velocity
data with the disclosed method can be performed through cloud
cover, as well as at night.
VI. Alternatives
In the above description, various functions were described as being
performed at either the base station or on the aircraft. Some of
the functions that were described as being performed at the base
station can be performed on the aircraft, and vice versa. For
example, the map matching process can be performed either at the
base station or on the aircraft.
The base station (100 in FIG. 1) that collects and processes the
traffic data received from the aircraft that fly over a geographic
area may be located in the same geographic area as the aircraft.
Alternatively, the base station may be located in another
geographic area. If the base station is located in another
geographic area, the data collected from the aircraft flying over
one geographic area are transmitted to the geographic area where
the base station is located. The data may be transmitted over any
suitable communications system, including a combination of wireless
and land-based communications networks. One base station may
collect and process the data from aircraft located in multiple
different geographic areas.
In connection with the above embodiments, it was indicated that
when scans of the roadways are being performed from the aircraft,
the scan pattern and the aircraft position were used to aim the
remote sensor at the appropriate locations along the roadways. In
addition, the geographic database used in the aircraft may include
data about special distinguishing landmarks to assist in
identifying the roads for which traffic measurements are to be
obtained. For example, the geographic database may include data
indicating the locations of tall or prominent buildings, towers, or
other features, located along the flight path. These features may
be easily detectable by appropriate aiming of the remote sensor
apparatus in the aircraft. Sensing these easily detectable
landmarks can help in determining the location and orientation of
the aircraft relative to the other features represented in the
geographic database (specifically, the roads). The detection of
distinguishing landmarks, can be used in conjunction with other
equipment in the aircraft, such as the positioning system, etc.
As mentioned above, the remote sensing apparatus may be operated
using a full sweep pattern (in which the entire area around the
aircraft is sensed and the pertinent vehicle velocity data are
extracted) or a targeted pattern (in which the remote sensing
apparatus is aimed precisely at specific locations along roads). If
the remote sensing apparatus is operated in a fully targeted
pattern, the need for additional map matching (i.e., post data
acquisition) may be reduced or eliminated because the map matching
step is essentially being performed before the data are acquired.
The remote sensing apparatus may also be operated in a mode that
combines a full sweep pattern and a targeted pattern.
In some embodiments, the aircraft used to collect the vehicle
velocity data are piloted. In alternative embodiments, the aircraft
may be unmanned or piloted from the ground.
In another embodiment, the scanning of locations along roads is
performed by an aircraft that maintains a motionless or relatively
motionless position over the geographic area. According to this
embodiment, the aircraft is of a type that has the ability to
remain relatively motionless over a single location. For example, a
lighter-than-air airship may be suitable. According to this
embodiment, the aircraft assumes an altitude that is high enough so
that locations along the roads in the entire geographic area can be
sensed from a single position. In this embodiment, the flight path
is essentially a single position. As in the other embodiments, the
remote sensing apparatus in the aircraft is aimed at the locations
along roads for which traffic information is sought and the traffic
flow is measured using an accurate digital map of the geographic
area. In a further version of this embodiment, a plurality of
aircraft may be used, each of which assumes a different motionless
position over the geographic area. In another alternative, one
aircraft may move between a series of successive different
motionless positions over the geographic area at which remote
sensing of locations along roads is performed. In yet another
embodiment, a combination of one or more motionless positions and
one or more moving position are used. As in the other embodiments,
an accurate determination of the actual position of the aircraft is
used to adjust the data obtained by scanning to compensate for any
deviation of the actual aircraft position from a desired position
at which the scans should be made.
It is intended that the foregoing detailed description be regarded
as illustrative rather than limiting and that it is understood that
the following claims including all equivalents are intended to
define the scope of the invention.
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